Measurements of high-energy radiation generation from laser-wakefield accelerated electron beams

Schumaker, W.; Sarri, Gianluca; Vargas, M.; Zhao, Zhen; Behm, K.; Chvykov, V.; Dromey, B.; Hou, Bixue; Maksimchuk, A.; Nees, J.; Yanovsky, V.; Zepf, Matthew; Thomas, Alexander; Krushelnick, K.

doi:10.1063/1.4875336

Cited by 39 publications

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“…This relatively low number can be easily understood if we consider that it would scale as N γ ∝ a 2 0 for a 0 1 [12]. The brilliance of this source is thus not higher than laser-driven bremsstrahlung source [5,9,10] (see Fig. 4 for a comparison of reported brilliance for different γ-ray sources).…”

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“…Bremsstrahlung sources are routinely used for medical applications, and exploit electron beams accelerated by linear accelerators (LINAC) [7]. Laser-driven bremsstrahlung sources, whereby the electron beam is generated via laser-wakefield acceleration (LWFA) [8] have also been recently reported [5,9,10]. However, the relatively broad divergence and source size limit the maximum brightness achievable with this technique and a more promising physical mechanism in this respect has been identified in Compton scattering.…”

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Ultrahigh Brilliance Multi-MeVγ-Ray Beams from Nonlinear Relativistic Thomson Scattering

et al. 2014

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We report on the generation of a narrow divergence (θ ≈ 2.5 mrad), multi-MeV (EMAX = 18 MeV) and ultra-high brilliance (≈ 2 × 10 19 photons s −1 mm −2 mrad −2 0.1% BW) γ-ray beam from the scattering of an ultra-relativistic laser-wakefield accelerated electron beam in the field of a relativistically intense laser (dimensionless amplitude a0 ≈ 2). The spectrum of the generated γ-ray beam is measured, with MeV resolution, seamlessly from 6 MeV to 18 MeV, giving clear evidence of the onset of non-linear Thomson scattering. The photon source has the highest brilliance in the multi-MeV regime ever reported in the literature.The generation of high-quality Multi-MeV γ-ray beams is an active field of research due to the central role of these beams not only in fundamental research [1], but also in extremely important practical applications, which include cancer radiotherapy [2,3], active interrogation of materials [4], and radiography of dense objects [5]. As an example, Giant Dipole Resonances of most heavy nuclei occur in an energy range of [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], exciting photofission of the nucleus.Different mechanisms have been proposed to generate γ-ray beams with these properties, including bremsstrahlung emission, synchrotron emission, and Compton scattering. Bremsstrahlung sources are routinely used for medical applications, and exploit electron beams accelerated by linear accelerators (LINAC) [7]. Laser-driven bremsstrahlung sources, whereby the electron beam is generated via laser-wakefield acceleration (LWFA) [8] have also been recently reported [5,9,10]. However, the relatively broad divergence and source size limit the maximum brightness achievable with this technique and a more promising physical mechanism in this respect has been identified in Compton scattering. Laserdriven electron beams with energy per particle of the order of the GeV are now routinely available in the laboratory [8], allowing for the possibility of all-optical and compact Compton-scattering sources [11,12].Previous investigations of laser-driven Compton scattering have mostly focused on the linear regime, i.e. whenever the dimensionless intensity of the laser pulse is less than 1 (a 0 < 1, whereby a 0 = eE L /(m e ω L c), with E L and ω L being the laser electric field and central frequency, respectively, and m e being the electron rest mass) [13,14] and report on γ-ray energies ranging from a few hundreds of keV [13] up to 3-4 MeV [14]. Three main factors can in principle be modified in order to increase the energy of the generated photons: the electron Lorentz factor (γ e ), the laser photon energy ω L , or the laser intensity a 0 . The mean energy of the generated photons can in fact be estimated as:with f (a 0 ) ≈ 1 for a 0 1 andLiu and collaborators recently reported on an increase in photon energy (up to 8-9 MeV) by frequency converting the scattering laser up to its second harmonic (thus increasing ω L in Eq. 1) [15]. However, using a higher laser frequency for scattering significantly ...

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Ultrahigh Brilliance Multi-MeVγ-Ray Beams from Nonlinear Relativistic Thomson Scattering

et al. 2014

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“…In order to experimentally observe EPB-driven plasma instabilities, it is crucial for the background gas within the second gas-cell to be fully ionised and form an ambient plasma, through which the EPB could interact. It must be noted here that, in addition to the EPB itself, the propagation of the ultra-relativistic electron beam through the solid target generates a bright and prompt flash of bremsstrahlung gamma-rays [15,23,24]. This burst of gamma-ray photons photo-ionises the background gas; in the case of a He gas, and for typical experimental parameters, it is straightforward to achieve full ionisation, with typical electron temperatures of the order of 10s of eV.…”

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General features of experiments on the dynamics of laser-driven electron–positron beams

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Dzelzainis

et al. 2018

Nuclear Instruments and Methods in Physics Research Section A:

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The experimental study of the dynamics of neutral electron-positron beams is an emerging area of research, enabled by the recent results on the generation of this exotic state of matter in the laboratory. Electron-positron beams and plasmas are believed to play a major role in the dynamics of extreme astrophysical objects such as supermassive black holes and pulsars. For instance, they are believed to be the main constituents of a large number of astrophysical jets, and they have been proposed to significantly contribute to the emission of gamma-ray bursts and their afterglow. However, despite extensive numerical modelling and indirect astrophysical observations, a detailed experimental characterisation of the dynamics of these objects is still at its infancy. Here, we will report on some of the general features of experiments studying the dynamics of electron-positron beams in a fully laserdriven setup.

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“…The beam was passed through a 1.5 cm thick Pb converter before the electrons/positrons were separated by a spectrometer magnet. The radiation length of Pb is ∼0.3 cm so the bremsstrahlung spectrum (as simulated by a Monte-Carlo code) has a similar number of photons as the number of electrons in the beam and an endpoint of ∼1 GeV [22]. After 4.2 m, the transmitted photons interacted with the 20 cm long Al rod surrounded by a highdensity polyethylene (HDPE) holder.…”

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Making pions with laser light

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Measurements of high-energy radiation generation from laser-wakefield accelerated electron beams

Abstract: Articles you may be interested in Improvements to laser wakefield accelerated electron beam stability, divergence, and energy spread using three-dimensional printed two-stage gas cell targets Appl.

Cited by 39 publications

References 34 publications

Ultrahigh Brilliance Multi-MeVγ-Ray Beams from Nonlinear Relativistic Thomson Scattering

Ultrahigh Brilliance Multi-MeVγ-Ray Beams from Nonlinear Relativistic Thomson Scattering

General features of experiments on the dynamics of laser-driven electron–positron beams

Making pions with laser light

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